Looking Deep, Deep Into Your Genes

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The findings of Sass, Silbergeld, and others indicate that mercury might play a role in the development of diseases involving immune system dysfunction. These diseases perhaps include autism -- think of Herbert's patients with their inexplicable collection of infections and allergies -- but also the spate of autoimmune disorders that we can't fully explain, from Graves' disease and rheumatoid arthritis to multiple sclerosis and lupus.
 "Do we need to reevaluate our fish advisories?" Silbergeld asks. "Are our regulations actually protecting the most sensitive people?" We target pregnant women and children because we've presumed that mercury's neurotoxic effects are most damaging to those whose brains are still developing. Sass and Silbergeld's findings don't contradict that assumption, but they do suggest that there might be other adults who are far more vulnerable than we'd realized -- who simply can't tolerate the more subtle effect the metal has on their immune system because of a peculiarity in their genetic makeup. Designing fish advisories for those people, whose sensitivities are coded in their DNA, is a challenge we've never tackled before.  Translating new findings about how chemicals affect gene activity into something of broader public health value will require that we understand precisely the tiny genetic differences among us that make one person or group of people more vulnerable than others to certain environmental exposures. One way to do that is by slightly modifying the gene chip to allow researchers to scan up to a million common genetic variants -- alternate spellings of genes, so to speak, that differ by just a single letter -- to look for small differences that might make some people more likely to get sick from a toxic exposure.  Our attempts to identify those who are most genetically susceptible to developing a particular disease as a result of environmental exposures have already yielded important insights. Patricia Buffler, dean emerita of the School of Public Health at the University of California, Berkeley, has found that children with a certain genetic variant may be susceptible to developing leukemia in high-traffic areas, where they're likely to be exposed to benzene compounds in auto exhaust. Other studies have found that a particular genetic variation in some women who drink chlorinated municipal water leads to an increased likelihood that they'll give birth to underweight babies. Still others have found that a specific version of an immune gene, HLA-DP, renders people vulnerable to the toxic effects of the metal beryllium, which causes a chronic lung condition in the genetically sensitive population. This particular vulnerability raises some sticky workplace issues. Toxic exposure to beryllium occurs almost exclusively in industrial settings where welders and other machinists come in contact with the metal while making defense industry equipment, computers, and other electronics. Should employers test their workers for genetic variants that may put them at risk for developing a disease? Could that information be used to bar someone from a job? Such ethical considerations, and their legal and public policy ramifications, will only multiply as we learn more.

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